Oscillograph galvanometer



Sept. 8,` 1953 M. E. MoRRow OSCILLOGRAPH GALVANOMETER Filed Sept. 1l, 1950 me.. J Hilf JNVENTOR. Marr/i7 .E Mar/0W ArmRA/EK lmwmwmmmv J I MW WM@ Patented Sept. 8, 1953 UNITED STATES PATENT OFFICE OSCILLOGRAPH GALVANOMETER Marvin E. Morrow, Tulsa, Okla., assignor to Midwestern Geophysical Laboratory, Tulsa, Okla., a corporation of Delaware Application September 11, 1950, Serial No. 184,156

3 Claims. 1

This invention relates to electrical devices for measuring currents or voltages and particularly adapted for use in connection with instruments for producing visual or photographic records of voltage or current changes. Oscillograph cameras employed in the eld of geophysics are usually provided with a bank of moving coil galvanometers each of relatively small nature requiring delicate manufacturing operations that normally render the cost of production relatively great.

There is accordingly a need by seismologists especially for an inexpensive, positively operating and long-lasting galvanometer that is capable of withstanding considerable abuse under various types of operating conditions.

It is one of the important objects of this in vention therefore, to provide a galvanometer having a coil mounting securing means that will effectively maintain the mirrors of the instrw ment in a set position while the securing means manipulated to the locked condition; having high resistance to corrosion; and of such nature as to present a positive, tight fit against entrance of the elements, such as dust and moisture, into the coil housing.

Another object of the instant invention is to provide a galvanometer having a novel coil mounting assembly formed to progressively in crease its sealing function as pressure is applied thereto and to maintain such seal during the time the instrument is in use, all without altering the pre-set position of the mirror with respect to the window of the device.

A further object of the invention hereof is to present a combination mounting and closure assembly that is readily releasable even after considerable use under normallyv damaging operating conditions.

A still further Iobject of this invention is to provide an assembly as above set forth that is less expensive than heretofore provided by virtue of reduction in cost of materials.

In the drawing:

Figure 1 is a substantially central, longitudinal sectional view of an oscillograph galvanometer made pursuant to my present invention.

Fig. 2 is an enlarged, fragmentary, sectional view taken on line II--II of Fig. 1; and

Fig. 3 is a cross-sectional view taken on line III- III of Fig. 2.

An elongated, hollow housing 4, of any suitable non-magnetic material is provided intermediate the ends thereof with a pair oi opposed pole members 6 and 8. I n normal use, the bank of galvanometers are mounted in a magnet assembly (not shown) and each nts within an opening with members 6 and 8 disposed between a pair of pole elements forming a part of the assembly. Electrical connection with the coil of the assembly is made through a conductible lock nut lil at one end of the housing 4.

A movable coil I2 is held between the members t and 8 by a, pair of opposed conductors I4 and I6, conductor I4 being secured to a spring IS and conductor I B having soldered attachment with head 20 of a mounting broadly designated by the numeral 22.

Spring I8 is carried by a polygonal, non-rotating reciprocable block 24 having ball and socket connection 26 with a threaded plug 28. Screw 28, as well as a threaded closure 30, are received by housing 4 by virtue of the latter being tapped as at 32 and a lock screw 34 holds block 24 in an adjusted position. The vibrations of conductor I4 induced by coil I2 are rendered visible through a transparent panel 3B forming a part of housing 4. Mirror 31 is mounted on coil l2 in the conventional manner.

Internal threads 38 in housing 4 adjacent the open end thereof opposite to closure 3!) receive a tubular bushing 4D that is in turn provided with an out-turned, annular flange 42 bearing tightly against the proximal end of housing 4. Bushing lill is formed from a solid, non-compressible material which has a high dielectric constant, preferably ivory or non-magnetic material lof like characteristics. Its external threads v44 terminate in spaced relationship to liange 42 whereby to present a tight intimate contact between bushing 4U and housing 4 at 46.

A collet 48 having a `cylindrical bore 523 is telescoped within the bushing 40 and is split as at 52. The bushing 40 and the collet 43 are provided with complemental, frusto-conical, interengaging surfaces 56 and 58 respectively with the base end of collet 48 disposed exteriorly of ange 42.

In addition to head 20, mounting 22 includes an elongated, integral stem 6D, threaded as at 62 remote from head 20, presenting an annular shoulder 64 of greater diameter than the inside diameter of bushing 40 adjacent the apex end thereof, but of less diameter than the inside diameter of housing 4.

Shoulder (i4 faces outwardly toward nut l0 oppositely to an annular, internal shoulder 66 which it abuts and formed by the innermost end of bushing 4i).

An internally tapped cup B8 threaded on stem i having wrench flats 'llll receives the base end of collet (i8 and has a continuous rim "l2 thereon, circumscribing collet (i8 and in sliding line contact with the proximal end of bushing lill.

It is noted that the apex end of collet i8 is spaced from shoulder 64 and that internally tapped lool; nut l@ is carried by the outer end of stem t2 in tight engagement with cup 68.

Interconnected coil i2, conductors l and I6, and mounting 22 are initially inserted into that end of housing i having threads 38 and the conductor il! is joined to spring I8 exteriorly of housing adjacent that end of the latter having threads 32.

Plug 28 is thereupon inserted in housing e to a point adjacent the inner end of threads 32v and the bushing it mounted in place with threads 38 and lie preferably sealed by use of a suitable cement. Collet 22 is next positioned in place and the cup S8 mounted on stem S5. As the cup ES is drawn tight, the rib lil thereof slides easily on the bushing te while head 2S moves tightly against shoulder E5. Simultaneously, collet wedges tightly in place to hold mounting 22 against rotation and te align the same ccaxially with the longitudinal a-Xisof housing Thereupon, lock nut iii is ailixed to hold cup E8 against loosening.

The operator then retracts the plug 28 to properly position coil l2, locks the block 2e by means of screw 3f?, and places closure 3! in place within housing il.

The speed of assembly and ease at which the same can be accomplished in now apparent. The tight t at that end of housing 4 adjacent threads 3S and the rigid mounting of coil l2 thereto assures absolutely against the entrance of dust, dirt, moisture and other deleterious elements into housing li.

Proper choosing of the materials for bushing 4) presents a holding means that will not yield to the compression that is exerted between head 2G and cup G8. And, by using substances for producing bushing di) that will have high diaelectric constant and a high resistance to corrosion and chemical damage, a highly eiiicient, fully satisfactory galvanometer is presented. After the mirror 3l and all associated parts are in place, mounting 22 will not be moved longitudinally by thrust created by tightening nut E8. The securing assembly above dened insures this result.

Further, bushing 4i! is Well reinforced not only by its surrounding housing ly but by its contained collet i8 and stem 50. Even after considerable use, the mounting 22 can be easily and quickly removed with no damaging effect what-- soever to the remaining component parts of the instrument.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In a galvanometer, an elongated, hollow housing provided with an open end; a tubular bushing secured Within the housing, the innermost end of the bushing presenting a rigid, stationary shoulder facing inwardly away from said open end; an elongated coil mounting having a head on one end thereof within the housing and extending outwardly from the housing through said bushing; means carried by the mounting eXteriorly of the housing for forcing said head tightly against the shoulder; and wedge structure in the bushing separate from the mounting and disposed for engagement by said means for aligning said mounting coaxially with the housing as the head is forced' against the shoulder.

2. In a galvanometer, an elongated, hollow housing provided with an open end; a tubular removably joined to the housing therewithin, the innermost end of the bushing presenting a rigid, stationary shoulder facing inwardly away from said open end; a tubular, split collet in the bushing, said collet and said bushing having complementary, kuste-conical, interengaging surfaces; an elongated coil mounting having a head on one end thereof within the housing and extending outwardly from the housing through said collet; and means' carried by the mounting exteriorly of the housing and bearing against the proximal ends of the bushing and the collet for forcing said head tightly against the shoulder and maintaining said collet in a position for aligning the mounting coaxially with the housing.

3. In a galvanometer, an elongated, hollow housing provided with an open end; structure presenting a frusto-conical surface in the housing and a stationary shoulder in the housing facing inwardly away from said open end; a shiftable, tubular collet in said housing, said collet having a surface complemental with and engaging said first-mentioned surface; an elongated coil mounting having a head on one end thereof within the housing and extending through said collet; and means carried by the mounting and bearing against one end of the collet remote from said head for forcing the latter tightly against the shoulder and maintaining the collet in a position for aligning the mounting coaxially with the housing.

MARVIN E. MORROW.

References Cited in the ille of this patent UNITED STATES PATENTS Number Name Date 2,268,526 Palmer Dec. 30, 1941 2,439,576 Morrow Apr. 13, 1948 FOREIGN PATENTS Number Country Date 4,276 Great Britain Jan. '7, 1893 

